Iodine: Radionuclides

Abstract

This article provides a review of iodine with regard to the basic chemistry, occurrence, speciation, separation, analysis, fate, and transport. Biogeochemical cycling of iodine in the environment is complex because iodine occurs in multiple oxidation states (ranging from −1 to +7), and inorganic and organic species may be hydrophilic, atmophilic, and biophilic. Organically bound iodine can be a significant fraction of total iodine in the atmosphere, biosphere, hydrosphere, and lithosphere. Nuclear‐fuel reprocessing facilities constitute the major source (>90%) of 129 I released to the environment. It has been recognized that 129 I is a very important dose contributor in risk assessment because of its tendency to concentrate in the human thyroid gland, long half‐life, and presumably high mobility. Speciation, input concentration, and residence time effects will influence the biogeochemical cycling of anthropogenic 129 I deposited on surface soils.

Isotopic Evidence Unveils Fossil Fuels Contribution to Atmospheric Iodine

“…Despite the vast majority of the iodine entering the brine during maturation, a significant amount was retained in the oil. For example, Alberta crude oil contains 7.77–9005 μg L –1 of iodine, which is significantly higher than the 1–3 μg L –1 in freshwater . This implies that when fuel oil is burned, a substantial amount of iodine is released into the atmosphere.…”

“…This is particularly noticeable in the Changchun and Chengdu data (Figure b,h). The main component of dust is mineral, which lacks iodine (<1.2 μg g –1 ) . When PM 2.5 is predominantly composed of dust, the proportion of coal- or fuel oil-sourced iodine is lower, and the particulate matter has an isotopic composition similar to that of iodine with the original atmospheric 129 I input, resulting in a much higher 129 I/ 127 I ratio than that of coal and fuel oil.…”

“…For example, Alberta crude oil contains 7.77−9005 μg L −1 of iodine, 38 which is significantly higher than the 1−3 μg L −1 in freshwater. 39 This implies that when fuel oil is burned, a substantial amount of iodine is released into the atmosphere. Additionally, fuel oils, similar to coal, were formed in ancient strata and exhibit a minimal 129 I/ 127 I signature.…”

“…The main component of dust is mineral, which lacks iodine (<1.2 μg g −1 ). 39 When PM 2.5 is predominantly composed of dust, the proportion of coal-or fuel oil-sourced iodine is lower, and the particulate matter has an isotopic composition similar to that of iodine with the original Similarly, fittings of dust contributions and 129 I/ 127 I followed y = c + a/(x + b), where "c" corresponds to a theoretical environmental baseline. Higher 129 I inputs may have caused a few data points to deviate from the overall data distribution; therefore, fittings in these cases were performed twice to remove the more discrete data points for a better assessment of the correlation quality for the remaining data.…”

Climate Control of Iodine Isotopic Composition Evidenced by Argentine Entisols Records

“…where R marine and R rock are the 129 I/ 127 I in the ocean, (1.5 ± 0.15) × 10 12 , and in the weathered rocks, respectively; I cosmo is the inventory of cosmogenic 129 I (atoms) deposited in 1 g soil or sediment from the atmosphere, and C marine is the proportion of ocean-emitted iodine in the sediments. Most soils and sediments have iodine content higher than 0.5 μg g 1 (Hu & Moran, 2011). Accordingly, assigning a much lower value, 0.1 μg g 1 , would derive an upper limit for I cosmo ⋅ X, 2 × 10 15 , which is still negligible compared with the other components in Equation 3.…”